Cooled furnace wall

ABSTRACT

A cooled furnace wall comprises a furnace shell with an inner and an outer side and cooling plates lining the inner side of the furnace shell. Each of the cooling plates has a plate body and protruding connection pieces for supplying the cooling plate with a coolant. The furnace shell has connection openings therein for interconnecting the connection pieces of adjacent connection plates from the outer side of the furnace shell. At least one of the connection pieces is formed by a tube bend that protrudes from an edge face of the plate body and that has a connection end to extending through one of the connection openings in the furnace shell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of International ApplicationNo. PCT/EP2004/050518 filed on Apr. 14, 2004. European PatentApplication No. 03 008 562.5 filed on Apr. 14, 2003 and LuxembourgPatent Application No. 91 025 filed on Jun. 5, 2003.

FIELD OF THE INVENTION

The present invention generally relates to a cooled furnace wall. Itrelates more particularly to a furnace wall comprising a furnace shellwith an inner side and an outer side and cooling plates lining the innerside of the furnace shell. Each of these cooling plates has a plate bodywith protruding connection pieces for a coolant. The furnace shell hasconnection openings therein, which enable to interconnect the protrudingconnection pieces of adjacent cooling plates from the outer side of thefurnace shell.

BACKGROUND OF THE INVENTION

It is well known to line the inner side of a furnace shell of ametallurgical furnace, in particular a blast furnace, with coolingplates. Such a cooling plate, also called “stave”, comprises arectangular, solid plate body with cooling passages therein. Connectionpieces, which protrude from the rear side of the cooling plate, debouchinto the cooling passages of the cooling plate. These connection piecesare led in a sealed manner through connection openings in the furnaceshell. At the outer side of the furnace shell, flexible metal tubes areused to interconnect the connection pieces of adjacent cooling platesand to connect the cooling plates to a cooling water distributioncircuit.

The plate body of such a cooling plate is made either from cast iron (inparticular modular cast iron) or from copper or a copper alloy, or morerecently also from steel. In cooling plates made from cast iron, thecooling passages are generally formed by cast-in U-shaped steel tubes,wherein the ends of a cast-in tube protrude from the rear side of theplate body as connection pieces. In virtually all cooling plates madefrom copper or steel, however, the cooling passages are directly formedin the solid cooling plate body.

DE 2 907 511 discloses a cooling plate which is made from a forged orrolled block of copper. The cooling passages in the copper block areblind bores produced by mechanical deep-drilling. The openings of theseblind bores are sealed off by soldering or welding plugs therein.Connecting bores are drilled from the rear side of the plate into theblind bores, and connection pieces for the coolant feed or coolantreturn are inserted into these connecting bores and soldered or weldedin place.

WO 98/30345 describes a process for manufacturing a cooling plate inwhich a blank of the cooling plate is produced by continuous casting.Inserts in the continuous-casting mould produce passages running in thecasting direction, which form the cooling passages in the finishedcooling plate. A plate is separated from the continuously-cast blank bymaking two cuts transversely with respect to the casting direction, thusforming two end faces, wherein the distance between these two end-facescorresponds to the desired length of the cooling plate. In the nextmanufacturing step, connection bores are drilled into the plate bodyperpendicular to its rear surface, so as to open into thethrough-passages. Thereafter connection pieces are inserted into theconnection bores and soldered or welded in place and the end-sideopenings of the passages are sealed off by soldering or welding plugstherein.

The processes described in DE A 2907511 and in WO 98/30345 both enablehigh-quality cooling plate bodies to be produced from copper or copperalloys. However, compared to cooling plates with cast-in cooling tubesor compared to mould-cast cooling plates, the finished cooling platesproduced by both processes have the drawback of relatively high pressurelosses in the transition regions between the connection pieces and thecooling passages.

WO 00/36154 proposes to reduce the pressure losses in copper coolingplates with cast or drilled cooling passages by inserting a shaped pieceinto a cut-out in the cooling plate body, so as to form a divertingpassage with optimised flow conditions for the cooling medium. However,this solution is relatively labour-intensive and results therefore inhigher production costs for the cooling plates.

DISCLOSURE OF INVENTION Technical problem

It is an object of the present invention, to optimise the connectionsbetween the cooling plates in a furnace wall as defined in the preamble.

OBJECTS AND SUMMARY OF THE INVENTION

According to a first aspect of the present invention, this object isachieved through the fact that a connection piece of a cooling plate isformed by a tube bend that protrudes from an edge face (i.e. a narrowside face) of the plate body and that has a connection end extendingthrough one of the connection openings in the furnace shell. Aconnection piece of this type may, for example, be formed by a 90° tubebend, a first end of which is inserted into an opening of a coolingpassage in the edge face of the plate body. In other words, theconnection piece no longer opens perpendicularly through the rear sideof the cooling plate body into the cooling passage, but rather in axialextension of the cooling passage through an edge face of the coolingplate body. The cooling fluid is consequently diverted within the tubebend connection piece itself, which causes relatively low pressurelosses.

It will also be appreciated that production of a cooling plate withcooling passages formed directly in a solid plate body is significantlysimplified by the present invention. In fact, the openings of thecooling passages in the edge faces of the cooling plate body no longerhave to be sealed by soldering or welding plugs therein, and there isalso no need to drill separate connection passages for the connectionpieces from the rear side of the cooling plate. In the process which isknown from DE-A-2907511, the blind bores can be replaced bythrough-bores, which simplifies cleaning of the drilled coolingpassages. Moreover, dead end sections (i.e. passage end sections throughwhich there is no flow), in which sand, weld beads and rust particlesnormally accumulate and/or air pockets or vapour bubbles form, areavoided, which will result in an improved cooling capacity and servicelife of the cooling plates. Also the cooling of the bottom and top endsof the cooling plates is significantly improved, since the coolingmedium now flows directly through these top and bottom ends.

Cooling plates with cooling passages directly formed in a solid platebody may, for example, comprise a continuously cast cooling plate bodymade from copper or a copper alloy with cast-in cooling passages, aforged or rolled cooling plate body made from copper or a copper alloywith drilled or milled cooling passages, or a cooling plate body madefrom steel with drilled or milled cooling passages. In the case of acooling plate body made from copper or a copper alloy, tube bends madefrom copper or a copper alloy or from stainless steel will normally beused. In the case of a cooling plate body made from steel, steel tubebends are preferred.

Generally, vertical cooling plates, i.e. cooling plates with verticallyrunning cooling passages, are used in the context of the presentinvention. It is however also possible to use horizontal cooling plates,meaning cooling plates with horizontally running cooling passages. Inthe case of vertical cooling plates, a cooling passage forms an openingin an upper or lower edge face of the cooling plate body. In the case ofhorizontal cooling plates, a cooling passage forms an opening in theleft-hand or right-hand edge face of the cooling plate body.

In accordance with the present invention, the tube bend connectionpieces of two adjacent cooling plates connected in series may lierelatively close together. This is of advantage with regard to thearrangement of the connection openings in the furnace shell and theinterconnection of the connection pieces.

The tube bend connection pieces of two cooling plates are preferablyconnected by means of flexible connection means. In accordance withanother aspect of the present invention, these flexible connection meansare accommodated in a sealed connection box which is arranged on theouter side of the furnace shell and is preferably closed off by means ofa removable blind flange. This eliminates the need for expensive, sealedtube passages through the furnace shell and results in significant timesavings when mounting the cooling plates. Furthermore, it will beappreciated that a connection box of this type may also be dimensionedin such a manner that a cooling plate can be removed from the furnaceand introduced into the furnace through the connection box.

The flexible connection means advantageously comprises a tubecompensation bend which connects the tube bend ends of two coolingplates in the connection box and compensates for differential movementsof the cooling plates. Compared to a conventional metal hose, a tubecompensation bend of this type produces significantly lower pressurelosses and moreover has a longer service life.

To reduce the distance between the edge faces of two adjacent coolingplates, the second ends of the tube bends of the first cooling plate andthe second ends of the tube bends of the second cooling plate may bearranged in a row. In this case, the flexible connection means may, forexample, comprise a bent tube segment which is arranged in theconnection box and is substantially in the shape of racing cyclehandlebars. A shape of this type ensures the required resilience toabsorb differential movements of the cooling plates.

As an alternative solution to a connection box, the connection openingin the furnace shell may for example be covered by a socket piece. Thelatter has for each connection end a separate through-opening, and eachof these connection ends is connected in a sealed manner to the socketpiece by means of a compensator.

In order to protect the tube bends with respect to the interior of thefurnace, a plate extension may be arranged in front of the tube bends atthe edge face of the cooling plate.

If there are two rows of cooling plates arranged directly verticallyabove one another, the vertical joins between the cooling platesbelonging to the upper row may be offset relative to the vertical joinsbetween the cooling plates belonging to the lower row. In thisarrangement, the tube bends of a cooling plate belonging to the lowerrow can be connected to the tube bends of two adjacent cooling platesbelonging to the upper row.

The edge face of the plate body from which the connection piecesprotrude is advantageously bevelled towards the inner side of thefurnace shell. This allows two cooling plates which are to be connectedby means of their connection pieces to be arranged significantly closertogether. Furthermore, the bent connection pieces lie in the shadow ofthe bevelled cooling plate edge and are therefore at least partiallyprotected from heat radiation from the furnace interior. If two coolingplates are to be connected, the opposite edge faces from which theconnection pieces protrude are advantageously bevelled in a mirrorimage, so that they delimit a wedge-shaped space which narrows towardsthe interior of the furnace.

To enable two cooling plates which are to be connected by means of theirconnection pieces to be arranged even closer together, the connectionpiece has, at the outlet from the edge face of the plate body, a firstcurvature in the mid-plane of the plate body and thereafter a secondcurvature in a plane which is perpendicular to this mid-plane of theplate body. The connection piece may advantageously be composed of a 30°tube bend and a 90° tube bend, the centre lines of which lie in twoplanes which are perpendicular to one another. Two adjacent coolingplates can then be arranged above or next to one another in such amanner that the outlet of a connection piece in one edge face of thefirst cooling plate and the outlet of a connection piece in an oppositeedge face of the second cooling plate lie axially opposite one another,wherein the first curvature of a bent connection piece of the firstcooling plate is directed in a first direction and the first curvatureof a bent connection piece of the second cooling plate is directed inthe opposite direction. In this embodiment, the second curvatures of thebent connection pieces advantageously define parallel planes ofcurvature, the distance between which corresponds to 1.1 to 1.5 timesthe tube diameter of the bent connection pieces.

A plug made from an elastic material, in which there arethrough-openings for the connection ends, is advantageously insertedinto a connection opening in the furnace shell. This plug advantageouslyhas a lateral securing flange which is clamped between cooling platesand furnace shell. At least two connection ends are guided through theplug into a connection box on an outer side of the furnace shell, wherethey are connected to one another by means of flexible connection means.To improve the sealing of the connection box with respect to theinterior of the furnace, a section of the connection box between theplug and the flexible connection means is advantageously sealed with afoamed sealing material. Moreover, the connection box may have aleak-test valve at its deepest point.

The present invention is also applicable to cooling plates which have atleast one cooling passage which is formed by a cast-in tube. (This isfor example the case with most cooling plates made from cast iron). Forthese cooling plates, at least one end of the tube protrudes from anedge face of the plate body and forms the tube bend connection piece.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention will now be described withreference to the accompanying drawings in which:

FIG. 1: is a longitudinal section through a first embodiment of a cooledfurnace wall;

FIG. 2: is a longitudinal section through a second embodiment of acooled furnace wall;

FIG. 3: is a plan view of a first arrangement of cooling plates in anembodiment of a cooled furnace wall;

FIG. 4: is a plan view of a second arrangement of cooling plates in anembodiment of a cooled furnace wall;

FIG. 5: is a plan view of a third arrangement of cooling plates in anembodiment of a cooled furnace wall;

FIG. 6: is a longitudinal section through a third embodiment of a cooledfurnace wall;

FIG. 7: is a longitudinal section through a first variant of theembodiment shown in FIG. 6;

FIG. 8 is a longitudinal section through a second variant of theembodiment shown in FIG. 6;

FIG. 9: is a longitudinal section through a third variant of theembodiment shown in FIG. 6;

FIG. 10: is a longitudinal section through a fourth embodiment of acooled furnace wall;

FIG. 11: is a longitudinal section through a first variant of theembodiment shown in FIG. 10;

FIG. 12: is a longitudinal section through a fifth embodiment of acooled furnace wall;

FIG. 13: is a longitudinal section as in FIG. 6, with further details;

FIG. 14: is a plan view of a connection box in which connection piecesof two cooling plates are connected to one another; and

FIG. 15: is a plan view of an arrangement of cooling plates withconnection boxes in accordance with FIG. 14;

FIG. 16: is a three-dimensional view of a first embodiment of aturbulator to be inserted in a cooling passage of a cooling plate;

FIG. 17: is a three-dimensional view of a second embodiment of aturbulator to be inserted in a cooling passage of a cooling plate.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION WITH REFERENCE TOTHE DRAWINGS

The furnace wall 10 shown in the drawings to illustrate the invention isa blast furnace wall cooled by means of cooling plates. In FIGS. 1 and2, reference numeral 12 denotes a furnace shell. An upper end of a lowercooling plate 14 and a lower end of an upper cooling plate 14′ can beseen on the inner side of the furnace shell 12. These cooling plates 14,14′ are affixed to the furnace shell 12 by means of threaded bolts 16and form a cooled lining of the inner side of the furnace shell 12. “D”denotes the vertical distance between the upper edge face 18 of thelower cooling plate 14 and the lower edge face 18′ of the upper coolingplate 14′. In the embodiments shown in FIG. 1 and FIG. 2, this distance“D” approximately corresponds to three times the thickness “E” of thecooling plates 14, 14′.

The cooling plates 14, 14′ shown in FIG. 1 and FIG. 2 have a solidcooling plate body 20, 20′ made from copper or a copper alloy. Verticalcooling passages 22, 22′ are arranged directly in this solid coolingplate body 20, 20′, i.e. they have, for example, been cast, drilled ormilled into the base material of the cooling plate body 20, 20′. Thesecooling passages 22, 22′ are formed as vertical through-passages whichextend parallel through the cooling plate body 20, 20′. It can be seenfrom FIG. 1 and FIG. 2 that the cooling passage 22 forms an opening 24in the upper edge face 18 of the lower cooling plate 14, and that thecooling passage 22′ forms an opening 24′ in the lower edge face 18′ ofthe upper cooling plate 14′.

Reference numerals 26 and 26′ denote thick-walled 90° tube bends madefrom copper which form connection pieces of the cooling plates 14, 14′.It can be seen that one end 28 of the lower tube bend 26 is welded orsoldered into the openings 24 in such a manner that the second end 30(also referred to as connection end 30) of the lower tube bend 26 facesa connection opening 32 in the furnace shell 12, and that one end 28′ ofthe upper tube bend 26′ is welded or soldered into the opening 24′ insuch a manner that the second end 30′ (also referred to as connectionend 30′) of the upper tube bend 26′ faces the same connection opening 32in the furnace shell 12. In this arrangement, the two tube bends 26 and26′ lie vertically above one another in the free space which is formedbetween the upper edge face 18 of the lower cooling plate 14 and thelower edge face 18′ of the upper cooling plate 14′. To shield the freespace 34 in which the tube bends 26 and 26′ are located with respect tothe interior of the furnace, a plate extension 36, 36′ is arranged bothat the upper edge face 18 of the lower cooling plate 14 and at the loweredge face 18′ of the upper cooling plate 14′, in each case towards theinterior of the furnace.

DETAILED DESCRIPTION OF THE INVENTION

In the embodiment shown in FIG. 1, the lower tube bend 26 is connectedto the upper tube bend 26′ by means of a compensation tube bend 40, thecompensation tube bend 40 being welded to the free ends 30, 30′ of thetube bends 26, 26′. This compensation tube bend 40 passes the coolingmedium (generally cooling water) out of the cooling passage 20 into thecooling passage 20′, wherein its resilience in the vertical directioncompensates for temperature-related changes in the distance “D”. Thecompensation tube bend 40 projects into a connection box 42 which isarranged on the outer side of the furnace shell 12 over the connectionopening 32 in the furnace shell 12. This connection box 42 is connectedin a gastight manner to the furnace shell 12 and is likewise closed offin a gastight manner by means of a removable blind flange 44. Afterremoval of the blind flange 44 one has direct access to the compensationtube bend 40 from the outer side of the furnace shell 12.

In the embodiment shown in FIG. 2, extended connection ends 46, 46′ ofthe tube bends 26, 26′ are led in a sealed manner out of the furnaceshell 12. For this purpose, the connection opening 32 in the furnaceshell 12 is covered by a socket piece 48 which forms a passage 49, 49′for each connection end 46, 46′. Each connection end 46, 46′ is in thiscase connected in a sealed manner to the socket piece 48 by means of acompensator 50, 50′. The compensators 50, 50′ (bellows compensators areillustrated in FIG. 2) must be designed so as to be able to absorblateral and angular movements of the connection ends 46, 46′. A commonprotective housing 52 surrounds the two compensators 50, 50′. In theembodiment shown in FIG. 2, the connection ends 46, 46′ will beinterconnected, for example, by means of a metal hose coupling as shownin FIG. 13. (The term “metal hose” shall also encompass a metallicallyreinforced synthetic hose).

FIG. 3 shows a first arrangement of cooling plates on the inner side ofthe furnace shell 12. The cooling plates 14, 14′ are located verticallyflush above one another, but the cooling plates of two adjacent columnsare vertically offset by half the height of a cooling plate. As aresult, the connection openings 32 in the furnace shell 12 are likewisevertically offset, so that the furnace shell 12 is weakened to a lesserextent. This is particularly important for the design variant indicatedin the right-hand column. In this case, the connection opening 132 inthe furnace shell 12 and the connection box 42 are dimensioned in such amanner that a cooling plate 14, after removal of the blind flange 44 anddisconnection of the tube connections, can be removed from the furnaceor introduced into the furnace through the connection box 42.

FIG. 4 shows a second arrangement of cooling plates 14, 14′ on the innerside of the furnace shell 12. These cooling plates 14, 14′ arepositioned in rows above one another, but the cooling plates of twoadjacent rows are offset by half the width of a cooling plate. In thisarrangement, the upper tube bends 26 belonging to a lower cooling plate14 are in each case connected to tube bends 26′ of two adjacent uppercooling plates 14′.

FIG. 5 shows a third arrangement of cooling plates 14, 14′ on the innerside of the furnace shell 12. These cooling plates 14 are likewiselocated in rows above one another, the cooling plates belonging to twoadjacent rows being slightly offset. It will be observed that the ends30 of the tube bends 26 belonging to the lower cooling plates 14 and theends of the tube bends 26′ belonging to the upper cooling plates lie ina row. As a result, the vertical distance “D” between the upper edgeface 18 of a lower cooling plate 14 and the lower edge face 18′ of anupper cooling plate 14′ is reduced (and now approximately corresponds totwice the thickness “E” of the cooling plates 14, 14′). In the coolingplates of the left hand side of FIG. 5, the tube bends 26, 26′ areconnected by means of fixed tube segments 60 which, in order to absorbtemperature-related movements between the cooling plates, aresubstantially in the shape of racing cycle handlebars. In the coolingplates on the right-hand side of FIG. 5, the tube bends 26, 26′ areconnected by means of metal hoses 62.

FIG. 6 shows a further embodiment of the cooled furnace wall. In thisembodiment, the two edge faces 18, 18′ of the cooling plates 14, 14′ outof which bent connection pieces 26, 26′ are led out of the plate bodies20, 20′ are bevelled in mirror-image fashion towards the inner side ofthe furnace shell 12, in such a manner that they delimit a wedge-shapedspace 69 which narrows towards the interior of the furnace. The angle abetween the respective rear side of the cooling plate 14, 14′ and thecorresponding edge face 18, 18′ is advantageously in the range from 105°to 150° and is preferably 120°. In the wedge-shaped space 69, the bentconnection pieces 26, 26′ are substantially shielded from the thermalradiation from the interior of the furnace. They are located, so tospeak, in the shadow of the edges of the cooling plates 14, 14′.Moreover, the wedge-shaped space 69 may be filled with a refractorymaterial, in which case, however, the expansion of the cooling plates14, 14′ and their connection pieces must not be excessively impeded.Since the bent connection pieces 26, 26′ are now relatively wellprotected from thermal radiation, they may also be made, for example,from stainless steel. In this context, it should be noted that tubebends made from stainless steel have better mechanical properties andlower prices than thick-walled tube bends made from copper.

FIG. 7 shows a modification to the embodiment shown in FIG. 6. The twoplate bodies 20, 20′ are arranged vertically above one another on theinner side of the furnace shell. The edge face 18 of the lower platebody 20 has a nose-like projection 70 facing the interior of thefurnace, which is bevelled parallel to the opposite edge face 18′ of theupper plate body 20′, so that this nose-like projection 70 and the edgeface 18′ of the upper plate body 20′ form a gap 72 which slopes from theinterior of the furnace upwards towards the inner side of the furnaceshell 12. This gap 72 which rises upwards towards the inner side of thefurnace shell 12 makes it more difficult, for example, for settlingburden to penetrate into the wedge-shaped space 69.

FIG. 8 shows a modification to the embodiment shown in FIG. 7. The edgeface 18′ of the upper plate body 20′ has a nose-like projection 70′facing the interior of the furnace, which is bevelled parallel to theedge face 18 of the lower plate body 20, so that this nose-likeprojection 70, and the edge face 18 of the lower plate body 20 form agap 72 which slopes from the interior of the furnace downwards towardsthe inner side of the furnace shell 12. This gap sloping downwards inthe direction of the inner side of the furnace shell 12 makes it moredifficult for hot gases to penetrate into the wedge-shaped space 69.

FIG. 9 shows a further modification to the embodiment shown in FIG. 7.In this case, the two bevelled edge faces 18, 18′ each have a nose-likeprojection 70, 70′ facing towards the interior of the furnace, whichnose-like projections overlap one another. In this case the twonose-like projections 70, 70′ are separated by a type of labyrinth gap74. The latter makes it more difficult for hot gases and settling burdento penetrate into the wedge-shaped space 69.

FIG. 10 shows a further embodiment of the cooled furnace wall. The lowercooling plate 14 comprises a plate body 20 made from copper or steel.However, the upper cooling plate 14′ comprises a plate body 20′ madefrom cast iron in which the cooling passages are formed by cast-in tubes76′. The end of a tube 76′ of this type is led out of the edge face 18′of the plate body 20′, where it forms a bent connection piece 26′ with aconnection end 30′ which is guided through the connection openings 32 inthe furnace shell 12. It will be noted that the edge face 18′ isbevelled at the front and at the rear, the bent connection piece 26′emerging from the edge face bevelled at the rear. The bevelling towardsthe interior of the furnace results in an improved transition betweenthe cooling plate 14′ made from cast iron and the thinner cooling plate14 made from copper or steel.

FIG. 11 shows a modification to the embodiment shown in FIG. 10. In thisembodiment, the upper plate body 20′ made from cast iron, like the lowercooling plate 14 made from copper or steel, has an edge face 18′ whichis bevelled exclusively at the rear. Since the two front sides of theplate bodies 20 and 20′ are flush, the gap between the rear side of theplate body 20 made from copper or steel and the furnace shell 12 iswider than the gap between the rear side of the thicker plate body 20′made from cast iron and the furnace shell 12. However, the gap betweenthe rear side of the plate body 20 made from copper or steel and thefurnace shell 12 can be reduced, for example, by a constriction in thefurnace shell (not shown).

FIG. 12 shows a further embodiment of the cooled furnace wall. Both thelower cooling plate 14 and the upper cooling plate 14′ comprise a platebody 20, 20′ made from cast iron in which the cooling passages areformed by cast-in tubes 76, 76′. The edge face 18, 18′ is in each casepartially bevelled at the rear, the tube bend 26, 26′ emerging from theedge face which is bevelled towards the rear.

FIG. 13 shows a cooling plate arrangement as in FIG. 6 with furtherdesign details. It can be seen that a plug 80 with through-openings forthe connection ends 30, 30′ of the bent connection pieces 26, 26′ hasbeen inserted into the connection opening 32 in the furnace shell 12.The plug 80 consists of an elastic material, so that it does notsignificantly impede the free expansion of the connection pieces 26, 26′and cooling plates 14, 14′. At its edge, it has an encircling securingflange 82 which is clamped between the cooling plates 14, 14′ and thefurnace shell 12. The connection ends 30, 30′ are guided through thethrough-openings in the plug 80 into the connection box 42, where theyare connected to one another by means of a flexible connection line 84with quick-acting couplings 86, 86′. Immediately behind the plug 80, apartial section of the connection box 42 is filled with a foamed elasticmaterial 83 around the connection ends 30, 30′. The rear end of theconnection box 42, which is not filled with foam and in which theconnecting line 84 is arranged, has a leak-test valve 88 at its lowestpoint. In the event of a leak in the connections between the connectionpieces 26, 26′, cooling water collects in the rear end of the connectionbox 42. The leak-test valve 88 can be used to check the connection box42 for the presence of leakage water without the blind flange 44 of theconnection box 42 having to be opened.

FIG. 14 shows a plan view of a connection box 42 in which a plurality ofconnection pieces 26, 26′ of two cooling plates 14, 14′ are connected toone another. It can be seen that each of the bent connection pieces 26,26′, at the exit from the edge face 18, 18′ of the plate body 20, 20′,first of all has a first curvature 102, 102′ in the mid-plane of theplate body 20, 20′ (=plane parallel to the plane of the drawing) andthen a second curvature 104, 104′ in a plane which is perpendicular tothe mid-plane of the plate body 20, 20′. The connection pieces 26, 26′shown are composed, for example, of a 30° tube bend and a 90° tube bend,the centre lines of which lie in two mutually perpendicular planes.

In FIG. 14, the cooling plates 14, 14 are positioned above one another,in such a manner that the outlet point of a bent connection piece 26 inan edge face 18 of the first cooling plate 14 and the outlet point of abent connection piece 26′ in an opposite edge face 18′ of the secondcooling plate 14′ lie axially opposite one another. The first curvature102 of a bent connection piece 26 of the first cooling plate 14 isdirected towards the right. By contrast, the first curvature 102′ of abent connection piece 26′ of the second cooling plate 14′ is directedtowards the left, i.e. in the opposite direction. The planes ofcurvature 106, 106′ of the second curvatures 104, 104′ are parallel toone another and have a spacing “d” between them which corresponds to 1.1to 1.5 times the tube diameter of the bent connection pieces (26, 26′).It will be noted that the double curvature of the connection pieces 26,26′ makes it possible for the two cooling plates 14, 14′ to be arrangedvery close together.

FIG. 15 shows an arrangement of cooling plates with connection boxes 42as shown in FIG. 14. Each of the connection boxes 42 can be used toinstall and remove a cooling plate 14, 14′. It will be seen how theconnection boxes 42 are offset in terms of height in order not toexcessively weaken the furnace shell 12.

It will be appreciated that the tube bend connection piece mayadvantageously be used to mount a turbulator into a cooling passage ofthe cooling plate. FIG. 16 and FIG. 17 show possible embodiments of sucha turbulator 200, 200′. The latter comprises a turbulator body 202, 202′and a ring-shaped fixing flange 204, 204′. The turbulator body 202, 202′is axially inserted into the cooling channel. The ring-shape fixingflange 204, 204′ bears on a shoulder surface in the opening of thecooling channel in the edge face of the cooling plate. It is blocked onthis shoulder surface by means of the connection piece, whose end isinserted into this opening and sealingly connected to the edge face bymeans of a welding or brazing joint. Such a turbulator will increaseefficiency of thermal transfer by adding a transversal velocitycomponent to the cooling fluid in the cooling channel.

1. A cooled furnace wall comprising: a furnace shell with connectionopenings therein, said furnace shell having an inner and an outer side;and cooling plates lining said inner side of said furnace shell, each ofsaid cooling plates having a plate body and protruding connection piecesextending through said connection openings for supplying said coolingplate with a coolant; wherein at least one of said protruding connectionpieces is a tube bend connection piece formed by a tube bend thatprotrudes from an edge face of said plate body and that has a connectionend extending through one of the connection openings in said furnaceshell where it is interconnected to a connection piece of an adjacentcooling plate from said outer side of said furnace shell.
 2. The furnacewall according to claim 1, comprising: a flexible connection meansinterconnecting said connection end of a tube bend connection piece froma first cooling plate to said connection end of a tube bend connectionpiece from a adjacent cooling plate.
 3. The furnace wall according toclaim 2, wherein: said connection opening in said furnace shell iscovered by a socket piece that has for each connection end a separatethrough-opening; and each of said connection ends is connected in asealed manner to said socket piece by means of a compensator.
 4. Thefurnace wall according to claim 2, wherein said cooling plates liningsaid inner side of said furnace shell comprise: a lower row of coolingplates separated by vertical joins; an upper row of cooling platesseparated by vertical joins and located vertically directly above saidlower row; wherein said vertical joins separating the cooling plates ofsaid upper row are offset relative to said vertical joins separating thecooling plates of said lower row.
 5. The furnace wall according to claim4, wherein: said tube bend connection pieces of a cooling plate of saidlower row are connected to said tube bend connection pieces of twoadjacent cooling plates of said upper row.
 6. The furnace wall accordingto claim 1, comprising: a connection box that is arranged on said outerside of said furnace shell above one of said connection openings;wherein connection ends of said tube bend connection pieces extend intosaid connection box where they are interconnected by means of flexibleconnection means.
 7. The furnace wall according to claim 6, wherein saidconnection box is sealed off by means of a removable blind flange. 8.The furnace wall according to claim 7, wherein said connection box isdimensioned so that one of said cooling plates can be removed from saidfurnace or introduced into said furnace through said connection box. 9.The furnace wall according to claim 8, wherein adjacent connectionopenings in the furnace shell are vertically offset.
 10. The furnacewall according to claim 6, wherein said flexible connection meanscomprises a compensation tube bend which is arranged in said connectionbox.
 11. The furnace wall according to claim 6, wherein said flexibleconnection means comprises a bent tube segment which is arranged in saidconnection box and is substantially in the shape of racing cyclehandlebars.
 12. The furnace wall according to claim 6, wherein saidflexible connection means comprises a metal hose which is arranged insaid connection box where it is coupled to said connection ends of apair of tube bend connection pieces.
 13. The furnace wall according toclaim 1, wherein: a plate extension is arranged at said edge face ofsaid cooling plate in front of said tube bend connection pieces, so thatit shields said tube bend connection pieces with respect to the interiorof the furnace.
 14. The furnace wall according to claim 1, wherein saidedge face of the plate body from which said tube bend connection pieceprotrudes is bevelled towards said inner side of said furnace shell. 15.The furnace wall according to claim 14, wherein said bevelled edge faceforms an angle of between 105° and 135° with respect to the rear side ofsaid cooling plate.
 16. The furnace wall according to claim 15, whereinsaid bevelled edge face forms an angle of approximately 120° with therear side of said cooling plate.
 17. The furnace wall according to claim14, wherein for two cooling plates which are interconnected by means ofsaid tube bend connection pieces, the opposite edge faces from whichsaid tube bend connection pieces protrude are bevelled in a mirrorimage, so that they delimit a wedge-shaped space which narrows towardsthe interior of said furnace.
 18. The furnace wall according to claim17, wherein: the plate bodies of said two cooling plates are arrangedvertically directly above one another, so that an upper edge face of thelower plate body is directly facing a lower edge face of the upper platebody; and said upper edge face of the lower plate body has a nose-likeprojection which is bevelled parallel to said lower edge face of theupper plate body, so that said nose-like projection and said lower edgeface of the upper plate body form a gap which slopes upwards towardssaid inner side of said furnace shell.
 19. The furnace wall according toclaim 18, wherein: the plate bodies of said two cooling plates arearranged vertically directly above one another, so that an upper edgeface of the lower plate body is directly facing a lower edge face of theupper plate body; and said lower edge face of the upper plate body has anose-like projection which is bevelled parallel to said upper edge faceof the lower plate body, so that said nose-like projection and saidupper edge face of the lower plate body form a gap which slopesdownwards towards said inner side of said furnace shell.
 20. The furnacewall according to claim 18, wherein the two bevelled edge faces eachhave a nose-like projection facing towards the interior of the furnace,and the two nose-like projections overlap.
 21. The furnace wallaccording to claim 1, wherein said tube bend connection pieces have atthe outlet from said edge face a first curvature in a mid-plane of saidplate body and thereafter a second curvature in a plane perpendicular tosaid mid-plane of said plate body.
 22. The furnace wall according toclaim 21, wherein such a tube bend connection piece is composed of a 30°tube bend and a 90° tube bend, the centre lines of which lie in planeswhich are perpendicular to one another.
 23. The furnace wall accordingto claim 21, comprising: two adjacent cooling plates, which are arrangedabove or next to one another in such a manner that the outlet of a tubebend connection piece in one edge face of the first cooling plate andthe outlet of a tube bend connection piece in an opposite edge face ofthe second cooling plate lie axially opposite one another; wherein: saidfirst curvature of a tube bend connection piece of said first coolingplate is directed in a first direction, and said first curvature of atube bend connection piece of said second cooling plate is directed inthe opposite direction.
 24. The furnace wall according to claim 23,wherein: said second curvature of said tube bend connection piece ofsaid first cooling plate and said second curvature of said tube bendconnection piece of said second cooling plate define parallel planes ofcurvature; and the distance between two of such parallel planes ofcurvature that are adjacent corresponds to 1.1 to 1.5 times the tubediameter of said tube bends.
 25. The furnace wall according to claim 23,wherein: the opposite edge faces of the two plate bodies are bevelled inmirror-image fashion, so as to delimit a wedge-shaped space whichnarrows towards the interior of the furnace; said connection end of atube bend connection piece of said first cooling plate extends throughsaid connection opening behind the bevelled edge face of said secondcooling plate; and said connection end of a tube bend connection pieceof said second cooling plate extends through said same connectionopening behind the bevelled edge face of said first cooling plate. 26.The furnace wall according to claim 1, comprising a plug made from anelastic material that is inserted into one of said connection openingsin said furnace shell.
 27. The furnace wall according to claim 26,wherein said plug has a lateral securing flange which is clamped betweensaid cooling plates and said furnace shell.
 28. The furnace wallaccording to claim 26, wherein: on said outer side of said furnaceshell, a connection box is arranged above said connection opening; atleast two connection ends extend through said plug into this connectionbox, where they are interconnected by means of flexible connectionmeans; and a section of said connection box between said plug and saidflexible connection means is sealed with a foamed sealing material. 29.The furnace wall according to claim 28, wherein said connection box hasa leak-test valve at its lowest point.
 30. The furnace wall according toclaim 1, wherein: at least one of said cooling plates lining said innerside of said furnace shell has at least one cooling passage which isformed directly in said plate body; said cooling passage forms anopening in said edge face of said plate body; and a first end of saidtube bend is inserted into said opening in said edge face.
 31. Thefurnace wall according to claim 30, further including a turbulatormounted in said cooling passage, wherein: said turbulator includes aturbulator body and a ring-shaped fixing flange; said turbulator body isaxially inserted into said cooling passage; said ring-shape fixingflange bears on a shoulder surface in said opening of said coolingchannel; and said ring-shape fixing flange is blocked on said shouldersurface by means of said first end of said tube bend that is insertedinto said opening in said edge face.
 32. The furnace wall according toclaim 1, wherein: at least one of said cooling plates lining said innerside of said furnace shell has at least one cooling passage which isformed by a cast-in tube; and at least one end of said tubes protrudesfrom an edge face of said plate body and forms said tube bend connectionpiece.